1. Field of the Invention
The present invention relates to, for example, a lens unit and a portable electronic device, and more particularly, it relates to the cooling structure of their image pickup element modules.
2. Description of the Related Art
Generally, in an electronic device of the above-mentioned type, when an image pickup element as an electronic component and a central processing unit (CPU) configuring a control circuit are internally mounted, it is requested to take thermal measures after they have been dust-proofed. As to the thermal measures, higher dust-proofness increases the temperature of the electronic component, while a higher noise level, in the case of an electronic camera apparatus, causes deterioration in image quality. Therefore, the above-mentioned thermal measures are especially one of the important issues due to recent enhanced performance of the image pickup element and CPU.
Thus, as such heat releasing structures, there have been proposed liquid-cooling and air-cooling type structures in, for example, Jpn. Pat. Appln. KOKAI Publication No. 02-143152, Jpn. Pat. Appln. KOKAI Publication No. 2006-332894, Jpn. Pat. Appln. KOKAI Publication No. 2006-174226 and Jpn. Pat. Appln. KOKAI Publication No. 2005-93848.
Jpn. Pat. Appln. KOKAI Publication No. 02-143152 discloses the liquid-cooling type configuration in which a cooling plate is brought in contact with the surfaces of integrated circuit elements installed on a circuit substrate, and, for example, cooling water is supplied to a micro cooling medium flow path to water-cool the cooling plate. Then, a thermally conductive deformable substance such as a compound having good thermal conductivity is interposed in a thermal junction between the cooling plate and the integrated circuit elements to increase a contact area, thereby attempting to achieve good thermal conductivity.
Specifically, a large number of integrated circuit elements are installed on one side of the circuit substrate such as a ceramic plate. Further, a liquid-cooling module disposed on the circuit substrate has a configuration in which a thermally conductive deformable substance, such as a compound having good thermal conductivity, is interposed between the cooling plate to which a cooling medium is supplied from the cooling medium flow path and the surfaces of integrated circuit elements. Then, the cooling plate and the integrated circuit elements are satisfactorily thermally joined together by the pressure of a spring. Moreover, liquid supply means comprises a cooling medium supply pipe coupled to the cooling medium flow path, an on-off valve and a mechanical pump.
Furthermore, Jpn. Pat. Appln. KOKAI Publication No. 2006-332894 discloses an image pickup device adopting an air-cooling method, and this image pickup device comprises a body side mount which is incorporated in a main body structure within a camera body and which supports a photography lens, a shutter disposed in an opening of the main body structure along an optical axis, an image pickup unit, etc. That is, as the image pickup unit, there are provided an image pickup element fixing plate fixedly supported on the main body structure, an optical low pass filter, a protective glass and a bare chip type image pickup element. In this image pickup element, the image pickup element fixing plate configuring a heat releasing plate is adhesively bonded and fixed to the non-image-pickup-side surface of the image pickup element, so that the distance in the optical axis direction from the surface of the body side mount to an image pickup surface (photoelectric conversion surface) of the image pickup device is accurately set. Thus, heat generated due to the operation of the image pickup element is released via the image pickup element fixing plate, such that the rising of the temperature of the image pickup element is suppressed.
Furthermore, Jpn. Pat. Appln. KOKAI Publication No. 2006-174226 discloses an image pickup unit with a hand movement correction function of an image pickup element rocking type, wherein an image pickup element comprising a package, a lead frame, a cover glass, etc. is mounted on a circuit substrate so that a heat absorbing surface of a cooling element such as a Peltier element may be in contact with an opening provided in the circuit substrate via a plastic sheet on the back surface of the package. A small heat releasing member is disposed between the back surface of the package and the heat absorbing surface of the cooling element, and a large heat releasing member is disposed on a case side, so that these members are thermally coupled to each other by a heat transmitting member.
Furthermore, Jpn. Pat. Appln. KOKAI Publication No. 2005-93848 discloses a cooling structure, wherein a heat storage configured by a heat storage member for storing heat using latent heat is inserted by a screw structure into a heat receiving portion of a cooling member made of a metal material in which a heat generator is installed, thereby achieving higher cooling efficiency as well as a size reduction of the cooling member.